1. Technical Field
The present invention relates to an intake system for a V-type multicylinder internal combustion engine.
2. Description of the Related Art
An intake system for a V-type multicylinder internal combustion engine has been proposed in, for example, JP 7-197865 A. This known intake system includes an air distribution case, namely, a surge tank, disposed between two banks set at an angle to form a V. Intake pipes extend respectively from the intake ports of a plurality of cylinders into the air distribution case and have open ends opening into the air distribution case.
The surge tank of the intake system disclosed in JP-A H7-197865 has an air inlet in one end thereof with respect to a direction parallel to the crankshaft. A throttle body supporting a throttle valve is connected to the air inlet of the surge tank. Air that has flowed through the throttle valve into the surge tank is sucked into the intake pipes arranged in a direction parallel to the crankshaft and is carried to the cylinders.
Since the air inlet is formed in one end of the surge tank with respect to a direction parallel to the crankshaft, the open ends of the intake pipes are at greatly different distances, respectively, from the air inlet with respect to the direction parallel to the crankshaft. Consequently, the amount of air sucked into the intake pipe nearer to the air inlet and that of air sucked into the intake pipe farther from the air inlet are different and the amount of air supplied into the cylinder nearer to the air inlet and that of air supplied to the cylinder farther from the air inlet are different. Thus, the amounts of air supplied to the cylinders are distributed in a wide range.
Since air flows through intake passages of different lengths into the cylinders, rambling intake noise is generated.